The present invention relates to a magnetic disk storage apparatus using a magnetic disk coated with a lubricant film to protect the disk from friction damage. More particularly, the present invention relates to an apparatus and method for suppressing the evaporation of the lubricant film in order to maintain a stabilized lubricant film on the disk during periods of long operating duration.
A large capacity magnetic disk storage with a high real density provides the main file for information processing systems. Recently, an air-tight, dust-free enclosure for the magnetic disk driving assembly of such a system generally has been used in order to achieve highly reliable and maintenance-free operation. Usually the magnetic disk driving assembly has a flying head. Before starting, the flying head rests on the surface of the disks. During start-up of the rotation of the disks, and during the landing of the flying head onto the disk surfaces, there exists sliding friction between the flying head and the surface of the disks. Such operation of the disk device is called a "contact start stop" or CSS system.
In order to obtain a higher recording density on the disks, a very thin recording medium film is formed by vacuum sputtering or plating technology on the magnetic disks. Therefore, to protect the thin film of recording medium from wearing by sliding friction and also to reduce the wear of the magnetic heads, a lubricant is necessary for the magnetic disks.
Usually, the lubricant is formed as a film on the surface of the disks. Solid or liquid material having excellent lubricating qualities, such as higher fatty acids, esters of higher fatty acid, higher alcohols, ether compounds, fluorides thereof and the like, are used for the lubricant material.
In a magnetic disk driving assembly with an air-tight enclosure, the temperature normally rises up to around 60.degree. to 70.degree. C. The heat is generated inside the enclosure due to the "windage loss" being generated by the friction loss of the air layer adjacent the rotating magnetic disks. The disks rotate at a speed of 3000 to 6000 revolutions per minute. As a result, the temperature of the disks is higher than that of the surrounding environment. This higher temperature accelerates the evaporation of the lubricant film formed on the disks.
In addition, lower flying height of the magnetic head; namely, small spacing between the magnetic medium and the magnetic head slider, is required to enhance recording density. For higher recording density of 40,000BPI to 50,000BPI, the thickness of the lubricant film on the magnetic disk is required to be as small as 100 .ANG.. Such a thin lubricant film is exhausted by evaporation in a relatively short operating period of time at the high temperatures described above. As a result, the stored information in the disks is often damaged due to the friction between the head slider and the magnetic medium. Furthermore, the wear durability of the head slider is unsatisfactory. Thus, the reliability and maintainability of such prior art storage devices has been unsatisfactory.